The Macadamia Nut is a medium-sized tree which can grow to approximately 20 m in height with a similar crown width, giving the tree a rounded shape. The leaves are simple, narrow-elliptical to narrow-oblong in shape, tough, dark green and occur on branchlets in groups of three. Leaves are 10?15 cm long. Juvenile leaves have a serrated edge but mature leaves have a smooth margin. The flowers are cream or creamy-white in colour and occur on racemes up to 30 cm long. The racemes originate at the leaf axil. The fruit are a hard brown nut encased in a green leathery outer shell with a 2?3 cm diameter. The smooth brown nut contains an edible kernel.
The Macadamia Nut grows in remnant rainforest, preferring partially open areas such as rainforest edges. However, this habitat is not continuously fit for the species.
In a survey of eight populations in the Cooroy-Maleny district of the Sunshine Coast, Barry and Thomas (1994) collated the following habitat information. The sites spanned a wide range of landforms including hill crests, hill slopes, scree slopes and foot slopes, gullies, benches and terrace plains. The slopes range from level to steep, with altitudes from 5?340 m above sea level. High nutrient alluvial and volcanic soils predominate often with considerable exposure of rock fragments or substrate, mostly basalt and diorite. The surface soils are uniformly dark, slightly acid (pH 5.5?6.5) and varying in texture from clayey-sand through various loams to silty-clay. All sites are well-drained, some excessively so.
The Macadamia Nut prefers to grow in mild frost-free areas with a reasonably high rainfall. There have been records of planted specimens bearing fruit as far south as Sydney.
Vegetation communities in which the Macadamia Nut is found range from complex notophyll mixed forest, extremely tall closed forest, simple notophyll mixed very tall closed forest to simple microphyll-notophyll mixed mid-high closed forest with Araucaria and Argyrodendron emergents.
The Macadamia Nut reaches maturity at around ten years, and has a juvenile period of over six years.
This species has been recorded flowering in January, March and June to November. Fruits have been recorded from November?January and March?April. Macadamia Nuts begin to produce viable nut loads at around 10 years of age. Reproduction is by seed, with a seed viability of 3?6 months. The seeds are eaten by mammals and are dispersed by stream. The plant resprouts when damaged.